I have photographed a waterfall, Roughting Linn for 30 years and never tire of it. I visit the place at least 4 times every year sometimes just to sit, look and enjoy. I don't always find something new to photograph but never repeat what I have already done. I have found it to be very stimulating because my approach always makes me look for angles etc that I have never used, consequently I am always having to "see" in different ways.
The best example that I have seen of revisiting the same subject was a one year series by John Blakemore, a British photographer, that concentrated on a single oak tree. He photographed it in all seasons and in all weather conditions and the final work is sublime but unfortunately the only publication of it is in a corporate book for the company who commissioned the work.